The present invention relates to a flock separating apparatus for use in sewage or sludge treatment, comprising an electrolytic cell and a separating tank, into which the flock developed in the electrolytic cell is delivered and in which the flock rises up through the action of a gas produced in electrolysis.
The treatment or purification of sewage and industrial process waters is conventionally (e.g. International Reference WO 89/06161) carried out by using flock separating tanks with air blown therein, so that the rising air bubbles carry the lighter solids to the surface as flock which can be removed. For example, the Patent publications U.S. Pat Nos. 4,673,494 and 4,294,697 disclose such a combination of an electrolytic cell and a separating tank such that the electrolytically produced flock can be brought up to the surface in the separating tank by means of a gas released in electrolysis. Such a combination does not allow the use of optimal cell and tank structures and dimensions, resulting in a poor separation efficiency. The prior known flock separating tanks are relatively shallow and have been aimed at a relatively large surface area.